JP5288342B2 - Electrode for plasma reactor - Google Patents

Description

  The present invention relates to an electrode for a plasma reactor used in an apparatus for removing components that are contained in flue gas discharged from factories, plants, internal combustion engines, and the like and that adversely affect the environment.

  Conventionally, for example, the amount of CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxide), and PM (particulate matter) contained in exhaust gas discharged from an automobile engine, particularly a diesel engine, is reduced. In order to reduce, a catalyst and DPF (diesel particulate filter) are used. However, in the case of DPF, if the internal PM increases by collecting PM, the flow of exhaust gas deteriorates, the exhaust resistance of the diesel engine increases, and as a result, fuel consumption and output decrease.

In view of such a situation, in recent years, it has been attempted to oxidize collected PM to remove it as gasification (CO ₂ ), or to reform exhaust gas to reduce the emission amount of PM or the like. ing. As one of such attempts, an exhaust gas purifying apparatus including a catalyst that uses a plasma reactor is known. For example, in the device described in Patent Document 1, two electrodes are provided, one of which is a porous electrode, plasma is generated between the electrodes by applying an alternating voltage to the electrodes, and the exhaust gas is generated in the plasma. Then, the soot particles in the exhaust gas are retained in the porous electrode by passing through the porous electrode, and the active oxygen such as ozone reacts with the soot particles by plasma.

Moreover, in the thing of patent document 2, in the catalyst element which carry | supports a catalyst component in the piezoelectric element provided with a piezoelectric material and an electrode, an electrode is made porous and an alternating voltage is applied from an electrode. Thus, a plasma-like state is generated near the surface of the piezoelectric body.
Special table 2001-522302 gazette JP 2004-237135 A

  By the way, in the thing of patent document 1, the porous electrode is formed of SiC (silicon carbide). However, since SiC has good mechanical stability, it is not always easy to process. For this reason, when forming an electrode according to the shape of the plasma reactor, for example, when forming it into a cylindrical shape as shown in FIG. 2 of Patent Document 1, it is a method of processing a flat metal plate material into a cylinder. It was difficult to form.

Moreover, in the thing of patent document 2, the electrode which uses stainless steel is shown. Stainless steel is mainly an alloy of iron and chromium, although excellent in workability as compared with SiC, it required a high discharge starting voltage in order to generate the plasma. For this reason, for example, in an automobile using a 12-volt battery as a power source, it is disadvantageous to generate a high voltage, and a material capable of generating plasma with a low discharge start voltage has been desired.

  Therefore, the present invention aims to eliminate such problems.

That is, the present invention is an electrode for a plasma reactor for purifying particulate matter (PM) in exhaust gas, and is disposed in a space for performing plasma discharge on a path through which exhaust gas flows, and includes exhaust gas containing PM. It is made of porous nickel or copper with holes that allow gas to pass through. When two electrodes are placed facing each other with a dielectric in between, the distance between the two electrodes is generated by the dielectric. The exhaust gas does not pass through the inside of the dielectric, and the hole of the electrode has a concave and convex shape between the inner walls or on the inner wall. In the portion, particulate matter contained in the exhaust gas is captured, but the exhaust gas itself can pass from the surface side of the electrode opposite to the dielectric to the surface facing the dielectric. Ah is, the exhaust gas is characterized that you move to the downstream side through the gap between the between the electrodes through the electrode dielectric.

  The term “porous” refers to a structure having at least a large number of through holes, and includes a structure having a large number of holes that do not penetrate. The term “through” means that the gas flowing in from one opening of the hole passes through the hole and flows out from the other opening. The through-hole is preferably located on the surface side where the opening into which the gas flows and the opening through which the gas flows out are different. Further, it is desirable that the through-hole has an inner cross-sectional dimension sufficient to capture particulate matter such as PM contained in exhaust gas discharged from a diesel engine. Such a through hole and a non-through hole may be either randomly or arbitrarily formed, or regularly formed with a predetermined interval.

With such a configuration, it is possible to generate plasma with a low discharge start voltage. As a result, it is possible to reduce power consumption. In addition, because it is porous, for example, in a plasma reactor for treating exhaust gas containing PM, PM is collected and the collected PM exhibiting an excellent thermal electron work coefficient is used as an electrode material. Can be used. For this reason, it becomes possible to improve the purification capacity of exhaust gas. Nickel or copper has an excellent thermionic work function, can be easily processed , and can be processed into a desired shape such as a shape other than a flat plate, such as a corrugated plate or a tube.

In order to efficiently perform uniform plasma discharge, it is preferable to provide a dielectric on at least one surface. The dielectric may be flat when porous nickel or copper is plate. The dielectric may be provided integrally with porous nickel or copper by coating. The dielectric coating is applied so that the opening of the hole in the electrode is not blocked and that the hole has a sufficient internal dimension to capture the particulate matter. The paired electrodes are arranged at a distance at which plasma discharge can be started, and exhaust gas flows into the space between the electrodes where plasma is generated. Application of dielectric to porous nickel or copper by coating can be applied reliably even if the electrode made of nickel or copper has a plate shape or a complicated shape such as a cylindrical shape. It becomes possible.

  The present invention is configured as described above, can generate plasma at a low discharge start voltage, and can keep power consumption low. In addition, because it is porous, for example, in a plasma reactor for treating exhaust gas containing PM, PM is collected and the collected PM exhibiting an excellent thermal electron work coefficient is used as an electrode material. The exhaust gas purification ability can be improved. Moreover, since it is nickel or copper, it can be processed easily and can be processed into a desired shape such as a corrugated plate shape or a cylindrical shape other than a flat plate.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, a plasma reactor electrode (hereinafter referred to as an electrode) 100 of this embodiment includes a plate-like electrode plate 1 made of porous nickel and a flat plate provided on one surface of the electrode plate 1. It is composed of a dielectric 2 having a shape.

  The electrode plate 1 has a shape in which there is almost no flat portion on each surface, and has a large number of through holes 3 penetrating from at least one surface to the other surface and not penetrating on each surface. It has a large number of concave portions 4 and a large number of convex portions 5. Each surface has a concavo-convex shape over almost the entire area to form a height difference, and the convex portion 5 becomes a portion where the potential is concentrated when a voltage is applied to the electrode plate 1, and the efficiency of plasma discharge is increased. It contributes to improving. The concave portion 4 is not necessarily required, and may be formed as a portion lower than the convex portion 5 by forming the convex portion 5.

  The through-hole 3 does not necessarily have to penetrate directly from one surface to the other surface. When incorporated in a plasma reactor, if the gas to be processed, such as exhaust gas containing PM discharged from a diesel engine on one surface side, can pass to the other surface side Good. In this case, the through-hole 3 does not necessarily have to be straight, and may be bent or branched into two forks or three forks. The through-hole 3 has an uneven shape on the inner wall as well as the surface, and can capture substances such as PM contained in the exhaust gas in the concave portion or between the inner walls. Therefore, the inner diameter or the inner dimension of the through hole 3 is set to a dimension that makes it easy for PM to capture and does not easily pass through the through hole 3. By forming the through hole 3 with such dimensions, the electrode plate 1 itself can function as a filter with respect to PM like a DPF. However, since it is not closed alternately like DPF, pressure loss becomes low.

  The size and shape of the recess 4 are not limited, but are preferably large enough to capture (collect) a large number of PMs relatively deeply.

  The dielectric 2 is set to a thickness equal to a distance sufficient to generate plasma when a predetermined voltage is applied to the electrode plate 3 when two electrode plates are arranged facing each other and used in a plasma reactor. is there. The dielectric 2 itself is not porous, and gas cannot pass through it to be processed in the plasma reactor.

  In such a configuration, as shown in FIG. 2, the electrode 100 and the electrode 200 made of only the electrode plate 1 are sandwiched between the dielectrics 2, in other words, the electrode plates 1 on both sides of the dielectric 2 facing each other in a plate shape. Are used in a plasma reactor. In this case, for example, in a plasma reactor that constitutes an exhaust gas purification device (or exhaust gas aftertreatment device) that purifies exhaust gas of a diesel engine, the exhaust gas is, for example, outside the electrodes 100 and 200, that is, the dielectric 2. It flows into the through hole 3 of the electrode plate 1 from the surface not sandwiched, passes through the electrode plate 1 and moves to the downstream side of the exhaust gas purification device through the gap between the electrode plate 1 and the dielectric 2. (In FIG. 2, the direction of movement of the exhaust gas is indicated by an arrow).

  When the exhaust gas passes through the electrode plate 1, almost all PM contained in the exhaust gas is captured in the through holes 3 of the respective electrode plates 1. That is, each electrode plate 1 functions as a filter for PM. Since the main element of PM is carbon particles, the trapped PM functions as a part of the electrode plate 1. For this reason, when a voltage is applied to the electrode plate 1, electrons are emitted from the electrode plate 1 itself, and electrons 1 are also emitted from the trapped PM, and plasma discharge is started. Therefore, plasma can be generated efficiently.

  Moreover, since the trapped PM is sequentially burned and removed by the generation of plasma between the electrode plates 1, the through holes 3 of the electrode plate 1 are not clogged, and the exhaust gas continuously reacts with the plasma. Even if supplied to the vessel, the function of the electrode plate 1 as a filter does not deteriorate. Therefore, the reactor opening ratio can be prevented from being lowered, and the fuel consumption and output of the diesel engine can be prevented from being lowered.

  Thus, the electrode plate 1 formed with a porous structure of nickel having a high thermoelectron work function functions as a filter and captures the surface of the uneven surface and the inner surface shape of the through-hole 3 and PM. Since the PM thus functioned as a part of the electrode plate 1, plasma discharge can be efficiently started. For this reason, the discharge start voltage applied to the electrode plate 1 can be lowered, and the power consumption can be reduced. In addition, since the electrode plate 1 has a concavo-convex shape over almost the entire surface, plasma can be generated between the electrode plates 1 almost uniformly, and the exhaust gas purification ability can be improved.

  As shown in FIG. 3, it was confirmed that the exhaust gas purification capacity, particularly the PM removal rate, was greatly improved when compared with the existing plasma reactor. The existing plasma reactor used for comparison uses an electrode in which a stainless steel electrode plate having grooves formed on the front and back surfaces and an alumina plate are used, and exhaust gas passes through the groove. Compared to such an existing plasma reactor, the plasma reactor using the electrode 100 and the electrode 200 of this embodiment in combination with the existing plasma reactor has a reactor opening ratio of about three times. The PM removal rate could be increased up to about 7 times. As a result, for example, in a plasma reactor incorporated in an exhaust gas purification device combined with a diesel engine, the reactor open ratio can be increased, so that the exhaust resistance of the diesel engine does not increase, and fuel consumption and output decrease are prevented. can do.

  In the above embodiment, the flat plate-shaped dielectric 2 has been described. However, the dielectric may be provided by coating (applying) an electrode plate made of porous nickel. The electrode plate itself for coating the dielectric may have various shapes and structures, such as the above-mentioned plate shape, or other corrugated plate shape, cylindrical shape, or wound structure. The dielectric is the surface of the electrode plate, that is, the front and back surfaces facing each other when the electrode plate is plate-shaped, the inner and outer surfaces and the surface coated with a wound structure, and the end surface coating corresponding to the mouthpiece, It may be any one that coats at least one surface of the electrode plate and the inner surface of the penetration. When coating the dielectric, the through holes in the electrode plate must allow gas to pass and capture PM. Therefore, the dielectric is coated so that the opening of the through hole is not blocked and the internal dimension is sufficient for the through hole to capture PM.

  As described above, when the electrode is coated on the electrode plate with the dielectric, when the electrode plate is installed in the plasma reactor, the paired electrodes are arranged with a distance at which plasma discharge can be started. And a plasma reactor is comprised so that exhaust gas etc. may pass through the space between the electrodes which plasma generate | occur | produces.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, there is a plasma reactor of a processing apparatus installed for a device that exhausts smoke containing PM, such as an exhaust gas purification device of an automobile, a flue gas processing device in a facility that emits smoke such as a plant, etc. Can be mentioned.

Sectional drawing which expands and shows the principal part of embodiment of this invention. The side view which shows the combination at the time of using the electrode of the embodiment for a plasma reactor. The graph which shows PM removal rate at the time of using the electrode of the embodiment for a plasma reactor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrode plate 2 ... Dielectric material 3 ... Through-hole 4 ... Recessed part 100 ... Electrode for plasma reactors 200 ... Electrode for plasma reactors

Claims (2)

An electrode for a plasma reactor for purifying particulate matter in exhaust gas,
It is arranged in a space where plasma discharge is performed on a path through which exhaust gas flows, and is made of porous nickel or copper having holes through which exhaust gas containing particulate matter passes,
In the case where two electrodes are arranged opposite to each other with a dielectric interposed therebetween,
The dielectric keeps the distance between the two electrodes sufficient to generate plasma, and the exhaust gas does not pass through the dielectric,
The hole of the electrode captures particulate matter contained in the exhaust gas between the inner walls or in the concave and convex portions of the inner wall, but the exhaust gas itself is the dielectric in the electrode. all SANYO the body can be passed from the opposite side to the side facing towards the dielectric,
An electrode for a plasma reactor in which exhaust gas passes through the electrode and moves downstream through a gap between the electrode and the dielectric . An electrode for a plasma reactor for purifying particulate matter in exhaust gas,
It is arranged in a space where plasma discharge is performed on a path through which exhaust gas flows, and is made of porous nickel or copper having holes through which exhaust gas containing particulate matter passes,
The hole captures particulate matter contained in the exhaust gas between the inner walls or in the concave and convex portions of the inner wall, but the exhaust gas itself can pass through,
Coated with a dielectric so that the opening of the hole is not occluded and the hole has sufficient internal dimensions to capture particulate matter;
An electrode for a plasma reactor in which exhaust gas flows into a space between the electrodes where the paired electrodes are arranged at a distance at which plasma discharge can be started and plasma is generated .

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